Police said they have detained migrants in three more cases – one of which was traced to an asylum centre.
It comes as legal programmes have been launched for migrants, addressing areas of sexual equality and freedom of speech.
The classes, launched in Bavaria, are voluntary, and officials say they were planned before widespread assaults on women were revealed.
Tensions in the country are at breaking point as protests and counter-protests over the New Year’s Eve attacks in Cologne spark riots.
Yesterday, a masked group of 200 barricaded buildings and smashed shop windows as they demanded action from authorities in the city of Leipzig.
And vigilante groups have attacked foreign migrants as ‘revenge’ for the sex assaults.
Three teenagers aged 15 from Syria have been arrested for rape after a 17-year-old girl was attacked in a public swimming pool in Munich on Saturday.
The trio allegedly surrounded the teen, with one of the boys groping her under her swimming costume and penetrating her, making the sex attack rape under German law.
The girl’s sister was also allegedly groped before they managed to flee to a lifeguard who called the police.
Because the asylum seekers were only 15, they were not remanded in custody and were released, and will be prosecuted under juvenile law.
Officers have also made an arrest for rape and attempted murder after a 24-year-old woman was attacked on Christmas Eve.
The alleged attacker, aged 20 from Morocco, was traced to an asylum seeker centre.
During the attack outside a cemetery in Gelsenkirchen the woman was approached from behind and beaten unconscious before being dragged into a cemetery and raped.
Local mayor Frank Baranowski said: “Violence against women is always despicable and criminal, and it is a great shame that this has been shown to be a case where the alleged attacker is from the ranks of the asylum seekers, who only a short time before were welcomed into our community here in Gelsenkirchen.
“This is not only a gross disregard for hospitality but also inhumane.
“This person will not only face the consequences of his actions if convicted, but also he has done severe damage to all those others who have fled their homes and will now be tainted because of what he has done.”
Police said the man arrested was apparently a member of the “Casablanca” band, identified as a group of thousands of North